1. Technical Field
The present invention is related to a method of processing a cavity of a core substrate.
2. Description of the Related Art
In order to manufacture an embedded substrate, in which an electronic device is embedded in a substrate, it is necessary to process a cavity, which is the space for mounting the electronic device, in the substrate. The cavity can be processed in the substrate by a punching method, which is a mechanical process using a CNC drill or a mold, a drilling method using laser (CO2 laser or YAG laser) and the like.
When the cavity is processed with a mechanical process, the size of the cavity is not precise, and the mechanical friction with the substrate can potentially cause defects such as burr, crack and whitening on an inner wall of the cavity. For this reason, the cavity is often processed by use of a laser drill.
In the conventional method, a circuit is formed on a core substrate, and then a cavity is formed by directly laser-drilling an exposed insulation layer. In this case, a laser beam removes a portion of the exposed insulation layer to form the cavity, but areas other than the cavity itself of the insulation layer are also damaged (deformed) by the laser beam. Moreover, the shape of a beam mask of the laser drill is transferred to the surface of the insulation layer, thereby lowering the precision of the cavity size.